Abstract

A practical laser Doppler velocimeter with optical fibers in the whole system was developed. The novel optical probe designed for this LDV is constructed of a graded-index rod lens attached to the end of an optical fiber. Since the laser beam from the probe is well collimated, the velocity accuracy and sensitivity are significantly improved. Mechanical vibration measurements were also carried out with this LDV; vibration amplitude down to 1.0 μm p-p can be measured at a frequency of 120 Hz with high accuracy.

© 1981 Optical Society of America

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References

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  1. F. Durst, A. Melling, J. H. Whitelaw, Principle and Practice of Laser-Doppler Anemometry (Academic, New York, 1976).
  2. S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
    [Crossref]
  3. T. Tanaka, G. B. Benedek, Appl. Opt. 14, 189 (1975).
    [PubMed]
  4. H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
    [Crossref]
  5. S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
    [Crossref]

1980 (1)

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

1977 (1)

S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
[Crossref]

1975 (1)

1974 (1)

S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
[Crossref]

Benedek, G. B.

Durst, F.

F. Durst, A. Melling, J. H. Whitelaw, Principle and Practice of Laser-Doppler Anemometry (Academic, New York, 1976).

Hoki, N.

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Kajiya, F.

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Koyama, J.

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Melling, A.

F. Durst, A. Melling, J. H. Whitelaw, Principle and Practice of Laser-Doppler Anemometry (Academic, New York, 1976).

Nishi, Y.

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Nishihara, H.

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Shibata, K.

S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
[Crossref]

Shibata, N.

S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
[Crossref]

Tanaka, T.

Tsujiuchi, J.

S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
[Crossref]

S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
[Crossref]

Ueha, S.

S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
[Crossref]

S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
[Crossref]

Whitelaw, J. H.

F. Durst, A. Melling, J. H. Whitelaw, Principle and Practice of Laser-Doppler Anemometry (Academic, New York, 1976).

Appl. Opt. (1)

Opt. Commun. (2)

S. Ueha, K. Shibata, J. Tsujiuchi, Opt. Commun. 10, 88 (1974).
[Crossref]

S. Ueha, N. Shibata, J. Tsujiuchi, Opt. Commun. 23, 407 (1977).
[Crossref]

Rev. Laser Eng. (1)

H. Nishihara, Y. Nishi, J. Koyama, N. Hoki, F. Kajiya, Rev. Laser Eng. 8, 426 (1980), in Japanese.
[Crossref]

Other (1)

F. Durst, A. Melling, J. H. Whitelaw, Principle and Practice of Laser-Doppler Anemometry (Academic, New York, 1976).

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Figures (9)

Fig. 1
Fig. 1

Schematic diagram of the LDV: OF, optical fiber; B.S., beam splitter; O.P., optical probe; S.A., spectrum analyzer; fo, original frequency of laser light; f, Doppler shift frequency.

Fig. 2
Fig. 2

(a) Optical probe constructed of an optical fiber and a graded-index rod lens. The lens is attached to the end of the fiber in a thin stainless tube. (b) Laser Doppler velocimeter.

Fig. 3
Fig. 3

Ratio α (= Δf/f) as a function of incident angle θ of the optical beam.

Fig. 4
Fig. 4

Spectra of Doppler frequency shift f for (a) optical fiber probe without a lens, (b) the proposed probe constructed of an optical fiber and a graded-index rod lens. The velocity of the object is 4.5 m/sec, and the angle θ is 60°.

Fig. 5
Fig. 5

Dependence of relative output amplitude V0 on distance between the probe end and the moving object. Emitting power P from the probe is 0.5 mW for both probes.

Fig. 6
Fig. 6

Dynamic range of the velocity. The velocity is plotted as a function of the Doppler frequency.

Fig. 7
Fig. 7

Experimental arrangement for mechanical vibration measurements: OF, optical fiber; UDC, ultrasonic diffraction modulator; B.S., beam splitter; O.P., optical probe; Amp., amplifier; VO, vibrating object; S.A., spectrum analyzer.

Fig. 8
Fig. 8

Doppler beat frequency for two different vibration amplitudes: (a) 10 μm p-p, (b) 100 μm p-p. Center frequency is 40 MHz.

Fig. 9
Fig. 9

Vibration amplitude vs frequency difference fd between maximum and minimum frequencies.

Equations (7)

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f = 2 | v | λ cos θ ,
f max = 2 | v | λ cos ( θ Δ θ ) ,
f min = 2 | v | λ cos ( θ + Δ θ ) .
α = f max f min 2 f = tan θ sin Δ θ .
Δ θ = tan 1 ( N 0 A a 2 ) ,
f = f b 4 π B f s λ sin ( 2 π f s t ) ,
f d = 8 π B f s λ .

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